Droopy Gorgonian Sea Plume - Needs Water??



Gorgonian Sea Plume (Pseudopterogorgia sp), Caribbean
Gorgonian Sea Plume (Pseudopterogorgia sp)
by B. N. Sullivan

We were swimming along the pretty reefs off the coast of West Caicos in the Turks and Caicos Islands, looking for things to photograph.  I spotted this Gorgonian Sea Plume at the edge of a patch reef.  The first thing I noticed was that it was quite tall -- with a height  of about two meters.  But the thing that really struck me was how droopy its branchlets looked. The spontaneous thought that popped into my head was that it looked like a large house plant that someone forgot to water!

That was a silly thought, of course, and it made me chuckle to myself at the time.  But when we were reviewing the photos I had taken on that dive, Jerry looked at this one and immediately said, "Hmm, needs water."  I told him I had thought the same thing when we were out there on the reef, and we both had a laugh about that.  So, from the start, our title for this photo has been "Needs Water."



Cerianthids: Marine animals that look like flowers



Cerianthid "tube anemone" - Hawaii
Cerianthid "tube anemone" - Hawaii
by B. N. Sullivan

The creatures pictured here look like anemones, but they are not true anemones.  They are Cerianthids, commonly referred to as ‘tube anemones’, which are taxonomically quite distinct from true anemones.

Cerianthids and true anemones do belong to the same phylum, Cnidaria, and the same class, Anthozoa, but tube anemones belong to the subclass Ceriantipatharia, a taxon that also includes the so-called ‘black corals’ (Antipatharia).

Dark-colored Cerianthid, Hawaii
Dark-colored Cerianthid, Hawaii
One of the visible features that distinguishes Cerianthid tube anemones from true anemones is the morphology of their tentacles.  Cerianthids have shorter tentacles in their centers, and longer tentacles around the margin.  The color of the shorter tentacles usually is different from that of the longer tentacles, making them look a lot like flowers (at least to me).

White Cerianthid, Hawaii
Side view of a Cerianthid, showing its tube
Cerianthids dwell inside a rubbery tube (thus the name tube anemone) which is built from mucus secreted by the animal.  The tube is embedded in mud or packed sand. When not feeding, or when disturbed, the animal retracts inside its tube for protection.

These creatures can be difficult to photograph for several reasons.  Most Cerianthids are relatively small; their crowns of tentacles are perhaps 5 cm (2 in) across, so it’s necessary to get very close to them in order to photograph them.  If the photographer accidentally touches one of the tentacles, piff! the critter retracts.  And although Cerianthids happily feed in gentle currents, any nearby turbulence — like that created by the photographer as he or she moves about — causes the critter to quickly go into hiding.

These tend to be deep-dwelling creatures — all of the examples in this post were photographed at depths greater than 40 meters (130 ft).  They are accustomed to low levels of ambient light at those depths, so Cerianthids do not take kindly to blasts of artificial light from a camera strobe.  At best, one or two shots of an individual is all that a photographer can hope for before all that is left to photograph is the tube!

Cerianthid retracted into its tube
Cerianthid retracted into its tube
All of the Cerianthid tube anemones pictured in this post were photographed off the west coast of Hawaii’s Big Island.  This post was adapted from an article I wrote several years ago for ScienceBlogs.com.

Scarlet Hermit Crab from the Cayman Islands


Scarlet Hermit Crab (Paguristes cadenati), Cayman Islands
Scarlet Hermit Crab (Paguristes cadenati), Cayman Islands
by B. N. Sullivan

Many small crustaceans look quite similar to one another, but it's hard to misidentify this little hermit crab.  A denizen of reefs in the Caribbean Sea, the brilliant coloring of the Scarlet Hermit Crab (Paguristes cadenati) sets it apart from other hermit crab species of that region.

These little crabs (about an inch long) inhabit old gastropod shells, and for some unknown reason, the shells they choose as their portable houses usually are pretty cruddy looking.  The one in the photo on this page is covered with a layer of coralline algae so thick that it almost looked like a stone, rather than a seashell.

Like many hermit crab species, these little guys are difficult to find during daylight hours.  At dusk they emerge from their hiding places in the reef and go about foraging for their food.  We spotted this individual during a night dive at Little Cayman island.

Most often, divers see only the crab's red legs and pale eyestalks poking out of the aperture of the shell in which they live.  This individual was cruising along across some coral, so we got to see a bit of the pretty speckled markings on its back, too.

The Scarlet Hermit Crab is a member of the Diogenidae family.  Comprised of more than 400 known species, the Diogenidae are the second-largest family of marine hermit crabs.

Hunting Together: A Bar Jack and a Southern Stingray


A Bar Jack and a Southern Stingray hunting together
by B. N. Sullivan

We spotted this pair of hunters in the Caribbean.  The dark colored fish in the photo is a Bar Jack (Caranx ruber). This fish makes its living as an opportunistic feeder.  In this instance, it is swimming a little above and behind a Southern Stingray (Dasyatis americana) hoping to snag a free lunch.

The stingray finds its food by rummaging in the sand, looking for little creatures to eat -- worms, small clams, tiny crabs, and such. To locate its prey, it fans away the top layer the sand by fluttering the wing-like tips of its body disc.

The crafty Bar Jack follows closely, letting the stingray do the excavating.  If the stingray uncovers something that looks tasty to the Bar Jack, the jack will snatch it in a lightning strike, then resume its position keeping watch over the stingray's shoulder, as it were.

We've seen Bar Jacks throughout the Caribbean.  In addition to pairing with hunting stingrays, we've also seen them following goatfish -- another species that digs around in the sand and rubble for food. 

By the way, the Bar Jack doesn't always look so dark. When it's not feeding, it is a handsome silvery blue color, with a black bar running along its back from its dorsal fin down to the lower lobe of its tail fin like a racing stripe.